X-Git-Url: http://git.megacz.com/?p=ghc-hetmet.git;a=blobdiff_plain;f=compiler%2Ftypes%2FTypeRep.lhs;h=db41403a4b46b009779dbc5e342d579b63e19cfb;hp=446341db80c52f872f10299d62ac1824f8b8949e;hb=914e415702a25a6e52ab1eaaf2aea233d6c6097e;hpb=fdf8656855d26105ff36bdd24d41827b05037b91

diff --git a/compiler/types/TypeRep.lhs b/compiler/types/TypeRep.lhs
index 446341d..db41403 100644
--- a/compiler/types/TypeRep.lhs
+++ b/compiler/types/TypeRep.lhs
@@ -145,11 +145,12 @@ data Type
 	                --    can appear as the right hand side of a type synonym.
 
   | FunTy
-	Type
+	Type		
 	Type		-- ^ Special case of 'TyConApp': @TyConApp FunTyCon [t1, t2]@
+			-- See Note [Equality-constrained types]
 
   | ForAllTy
-	TyCoVar         -- ^ Type *or* coercion variable; see Note [Equality-constrained types]
+	TyCoVar         -- Type variable
 	Type	        -- ^ A polymorphic type
 
   | PredTy
@@ -183,21 +184,9 @@ The type   forall ab. (a ~ [b]) => blah
 is encoded like this:
 
    ForAllTy (a:*) $ ForAllTy (b:*) $
-   ForAllTy (wild_co : a ~ [b]) $
+   FunTy (PredTy (EqPred a [b]) $
    blah
 
-That is, the "(a ~ [b]) =>" part is encode as a for-all
-type with a coercion variable that is never mentioned.
-
-We could instead have used a FunTy with an EqPred on the 
-left.  But we want 
-
-  * FunTy to mean RUN-TIME abstraction,
-    passing a real value at runtime, 
-
-  * ForAllTy to mean COMPILE-TIME abstraction, 
-    erased at runtime
-
 -------------------------------------
  		Note [PredTy]
 
@@ -567,9 +556,7 @@ instance Outputable name => OutputableBndr (IPName name) where
 	-- OK, here's the main printer
 
 ppr_type :: Prec -> Type -> SDoc
-ppr_type _ (TyVarTy tv)         -- Note [Infix type variables]
-  | isSymOcc (getOccName tv)  = parens (ppr tv)
-  | otherwise		      = ppr tv
+ppr_type _ (TyVarTy tv)	      = ppr_tvar tv
 ppr_type p (PredTy pred)      = maybeParen p TyConPrec $
                                 ifPprDebug (ptext (sLit "<pred>")) <> (pprPredTy pred)
 ppr_type p (TyConApp tc tys)  = pprTcApp p ppr_type tc tys
@@ -605,17 +592,22 @@ ppr_forall_type p ty
     split2 ps (PredTy p `FunTy` ty) = split2 (p:ps) ty
     split2 ps ty		    = (reverse ps, ty)
 
+ppr_tvar :: TyVar -> SDoc
+ppr_tvar tv  -- Note [Infix type variables]
+  | isSymOcc (getOccName tv)  = parens (ppr tv)
+  | otherwise		      = ppr tv
+
 -------------------
 pprForAll :: [TyVar] -> SDoc
 pprForAll []  = empty
 pprForAll tvs = ptext (sLit "forall") <+> sep (map pprTvBndr tvs) <> dot
 
 pprTvBndr :: TyVar -> SDoc
-pprTvBndr tv
-  | isLiftedTypeKind kind = ppr tv
-  | otherwise             = parens (ppr tv <+> dcolon <+> pprKind kind)
-  where
-    kind = tyVarKind tv
+pprTvBndr tv 
+  | isLiftedTypeKind kind = ppr_tvar tv
+  | otherwise	          = parens (ppr_tvar tv <+> dcolon <+> pprKind kind)
+	     where
+	       kind = tyVarKind tv
 \end{code}
 
 Note [Infix type variables]